The present invention relates to a rotor and a motor.
A so-called Lundell type rotor (see e.g., Japanese Laid-Open Utility Model Publication No. 5-43749) is known as a rotor used in a motor. The Lundell type rotor includes two rotor cores and a field magnet. The rotor cores are combined with each other and each include a plurality of claw-poles arranged along a circumferential direction. The field magnet is arranged between the two rotor cores so that the claw-poles alternately function as different poles. Such a rotor includes a rotation shaft inserted through and fixed to each of the two rotor cores to integrally rotate the rotation shaft and the rotor core.
In the Lundell type rotor, the two rotor cores and the field magnet arranged in between are adhered and fixed to one another with an adhesive. Thus, an adhesive layer (layer of adhesive) between the rotor cores and the field magnet produces a magnetic resistance. The magnetic resistance between the rotor cores and the field magnet increases as the thickness of the adhesive layer increases. This lowers the motor performance, that is, decreases the motor output. When reducing the thickness of the adhesive layer and decreasing the gap (distance) between the rotor core and the field magnet to avoid such a situation, it becomes difficult to obtain the desired adhesive force.
Further, in the Lundell type rotor, the magnetic flux extending from the field magnet to the claw-poles of the rotor cores functions as an effective magnetic flux that generates torque for the rotor. In contrast, the magnetic flux extending from the rotor cores to the rotation shaft is a short-circuit magnetic flux. The effective magnetic flux decreases the short-circuit magnetic flux and thereby lowers the motor output. In the Lundell type rotor, a magnetic path extending from the field magnet via the rotor cores to the rotation shaft has a tendency of being shorter than the magnetic path extending from the field magnet to the claw-poles. Thus, the short-circuit magnetic flux from the rotor cores to the rotation shaft has a tendency of increasing, and the problem of reduction in the motor output becomes especially prominent.